CICLOPS: Cassini Imaging Central Laboratory for OPerationS

Sampling Saturn and a Shadow
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Cassini shows a section of Saturn and its rings which includes a special treat made possible as the planet approaches its August 2009 equinox: the shadow of a moon cast on the rings.

The novel illumination geometry created as Saturn approaches its August 2009 equinox allows moons orbiting in or near the plane of Saturn's equatorial rings to cast shadows onto the rings. These scenes are possible only during the few months before and after Saturn's equinox which occurs only once in about 15 Earth years. To learn more about this special time and to see movies of moons' shadows moving across the rings, see PIA11651 and PIA11660.

The moon casting the shadow, Tethys, is not shown in the image. In the left-most part of the top of the image, Saturn is overexposed where it is lit by the sun. The rest of Saturn shown here is dimly lit by ringshine and light scattered through the rings. See PIA09912 for an image of Saturn under similar lighting.

Four background stars can be seen in the image.

This view looks toward the unilluminated side of the rings from about 52 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on June 15, 2009. The view was acquired at a distance of approximately 1.8 million kilometers (1.1 million miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 89 degrees. Image scale is 103 kilometers (64 miles) per pixel.

The Cassini Equinox Mission is a joint United States and European endeavor. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini Equinox Mission visit, and

Credit: NASA/JPL/Space Science Institute
Released: August 13, 2009 (PIA 11557)
Image/Caption Information
  Sampling Saturn and a Shadow
PIA 11557

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Alliance Member Comments
Dragon_of_Luck_Mah_Jonng1971 (Aug 14, 2009 at 6:03 PM):
Tethys' shadow is very long in this picture -- that's special.